Two major types of micropackaging or microcontainment systems have been developed for packaging and containing active liquids, fluids, and solids in the form of free-flowing beads, particles, or powders. In microencapsulation, small droplets of the active or functional liquid or solid are coated with a continuous film of polymeric material. Microencapsulation is accomplished by a coacervation process. The microcapsule wall-forming liquid polymer or coating referred to as the coacervate is deposited on droplets or particles of the active liquid or functional ingredient which are in turn dispersed in a liquid vehicle or carrier. The wall coating forms during controlled physical mixing of the liquid vehicle, functional ingredient, and coating material or coacervate. The liquid coating material is solidified while the temperature of the liquid carrier is lowered at a specific pH. The process of microencapsulation and formation of microcapsule systems is further described in the Encyclopedia of Chemical Technology, Vol. 13, J. A. Herbig, "Microencapsulation", pp. 436-456, John Wiley & Sons, Inc., 2nd edition, 1967, and various United States patents including U.S. Pat. No. 2,969,330, U.S. Pat. No. 3,137,631, U.S. Pat. No. 3,341,466, U.S. Pat. No. 3,516,943 and U.S. Pat. No. 3,415,758.
In entrapment systems, the active liquid, ingredient, or functional material is contained by sorption within a microscopic polymeric matrix or lattice. The polymer lattice containment results in conversion, for example, of liquids, waxes, or solids into free-flowing particles.
Such micropackaging and microcontainment systems are applicable for storage and protection of active ingredients both liquid and solid, particularly where volatilization otherwise reduces the life or changes the character of the functional material. Micropackaging by encapsulation or entrapment protects the active liquids or solids from deterioration and exposure to air or even light, and increases longevity. For example, micropackaging enhances and improves the fidelity and longevity of emollients, fragrances, and oils. The micropackaging can be designed to provide slow release of a controlled ingredient, long-lasting continuous release by diffusion, or other sustained release patterns.
The micropackaging containment walls of the microcapsules or entrapping lattices may be constructed of a variety of materials to impart a variety of wall characteristics, elastic, rigid, fragile, or tough. Generally the microcontainment walls are sufficiently fragile or frangible to break in response to desired stresses and release the active ingredient or functional liquid or solid. For example, the container walls are typically designed to break in response to a desired level of rubbing or abrading, heating, light exposure, biodegradation, dissolving of the wall, diffusion, pH change, etc.
Polymer entrapment systems are available from Wickhen Products, Inc., Big Pond Road, Huguenot, N.Y., 12746, under the trademark POLYTRAP.TM.. Typical polymer entrapment particles range in particle size from less than 45 microns to, for example, 3,000 microns, that is from powders to beads. The characteristics of the entrapment materials may be varied according to the lattice wall copolymers and the ratio or percentage of copolymers comprising the particles.
Microencapsulation systems are available from, for example, QMAX Technology Group, P.O. Box 1509, 125 Bacon Street, Dayton, Ohio, 45402, for a variety of products. For example, microcapsules containing minute liquid droplets of essential fragrance oils are available, referred to as "microencapsulated fragrances". Microencapsulated inks and coatings are available for printing and advertising purposes. A variety of cosmetic products are also microencapsulated for various applications. Custom order coacervation microencapsulation techniques are available for any active ingredient on a task basis.
Typical microcapsule size range may be, for example, 40 to 100 microns, though particle size can be controlled from 5 microns to 5,000 microns. The encapsulation coacervate may be typically gelatin, PVA, or urea formaldehyde according to the application. The gelatin encapsulation systems are used for food additives and approved by the FDA.
U.S. Pat. No. 4,514,461 describes a method for producing a fragrance impregnated fabric by mechanically spraying fragrance microcapsules in combination with a liquid binder into the fabric. The fabric is then passed between heated rollers to insure deep and uniform penetration of the microcapsules into the interstices of the fabric. The fabric is either woven or nonwoven and the microcapsules are sufficiently fragile or frangible to break upon rubbing with normal hand pressure to liberate a fragrance or disinfectant. A deodorizer fabric is therefore provided for a variety of applications, such as medical supplies, etc. In U.S. Pat. No. 4,254,179 a method is described for impregnating a porous foam product with microencapsulated fragrance by depositing the microcapsules on one surface of the foam, supplying heat to the foam, and applying a vacuum to the opposite surface of the foam. The microcapsules are thus mechanically forced and distributed through the foam substrate.
A disadvantage of the prior art methods of distributing microencapsulated and micropackaged active ingredient particles through a fabric or foam substrate or matrix is that the forceful mechanical handling of the frangible microcapsules and lattices results in mechanical breakage with premature release of the active liquids or solids. However, U.S. Pat. No. 4,254,179 teaches that the mechanical loss accompanying the mechanical methods is superior to the addition of microcapsules during manufacture of the foam sheet or log because most of the microcapsules otherwise rupture due to the heat and pressure created in processing the foam, immediately liberating and losing much of the fragrance. A further disadvantage of the prior art mechanical methods of distributing micropackaged particles in fabric and foam substrates is that bonding is not assured and particles may be lost in handling.